1. Field of the Invention
The present invention relates to a process for preparing a magnetic recording medium. More particularly, it relates to a process for preparing a continuous thin layer type magnetic recording medium having a Co-Ni-P type thin magnetic layer.
2. Description of the Prior Art
Recently, a continuous thin layer type magnetic recording medium having a metallic thin magnetic layer has been considered to be important. It has been known that a Co-Ni-P type thin metallic layer as one of the thin magnetic layers of such continuous thin layer type magnetic recording media has excellent coercive force and squareness ratio. Heretofore, the Co-Ni-P type thin magnetic layer of the magnetic recording medium has been usually prepared by a plating process such as an electro-plating process and a chemical plating process. However, various disadvantages are found in such plating processes. Firstly, an adhesiveness of the thin layer to a substrate and a mechanical strength of the membrane are low to cause the wearing and peeling-off of the thin layer by friction of a magnetic head thereby changing the magnetic characteristics such as reduction of output characteristics. In order to overcome the disadvantages, a protective layer is formed on the surface of the thin magnetic layer. However, an increase of an effective gap between the magnetic layer and the magnetic head causes to increase a spacing loss and to reduces the recording and reproducing output.
Secondly, the flatness of the thin magnetic layer is inferior and the output in the high frequency region, is disadvantageously reduced.
Thirdly, the thin magnetic layer is contaminated by an alkali metal ion, an acid or a base in the plating bath whereby the magnetic characteristics of the thin magnetic layer are changed and deteriorated. Sometimes, the magnetic head is disadvantageously corroded.
Fourthly, the third harmonic distortion at 333 Hz is remarkably large in the application of an audio tape though the reason is not clearly found. These disadvantages are serious in the practical use.